In recent years, compact but large-capacity electrochemical devices that can be used for mobile phones, notebook personal computers and other portable electronics devices are drawing attention. Known examples of these electrochemical devices include, among others, electrical double-layer capacitors and lithium-ion capacitors.
Among others, Japanese Patent Laid-open No. Hei 6-176979 (Patent Literature 1) proposes one example of such an electrochemical device, or specifically a solid electrolytic capacitor that offers a larger capacity without losing such features as compactness and light weight. As shown in FIG. 7, a capacitor element 120 described in Patent Literature 1 has: an anode body 102 constituted by small unit areas dividing the entire anode body into multiple sections and on which an oxide film layer 104 and solid electrolytic layer 106 are formed; and a wire conductor 110 which is flexible and constituted by a conductor 112 whose surface is covered with an insulation layer 114, wherein the conductor 112 is exposed in an area overlapping with the solid electrolytic layer 106. This capacitor element 120 has the wire conductor 110 sandwiched between the solid electrolytic layers 106 formed by folding the anode body 102, and is structured in such a way that the exposed conductor 112 and solid electrolytic layer 106 are electrically connected via a conducting body 118. This capacitor element 120 has a high internal resistance because one end of the folded wire conductor is used as a lead terminal.
Japanese Patent Laid-open No. Hei 9-7893 (Patent Literature 2) proposes an electrical double-layer capacitor having a large capacitance and low internal resistance. As shown in FIG. 8, this electrical double-layer capacitor has an element constituted by: a pair of current collectors constituted by two strip-shaped conductors 219a, 219b that are folded alternately, polarizable electrodes 212 formed on the laminated surfaces of the current collectors, and a separator 203 provided between the adjacent polarizable electrodes 212. The electric double-layer capacitor thus structured needs a lamination process for each element, which is not suitable for mass production.
Japanese Patent Laid-open No. 2002-157997 (Patent Literature 3) proposes a folded lithium-ion battery that can be manufactured in a simple process, and method of manufacturing the same. Under this manufacturing method described in Patent Literature 3, as shown in FIG. 9 a negative-electrode sheet 301 is created by applying an active material 304 on strip-shaped uncoated areas 307 provided on both sides of a long negative-electrode current collector. On both sides of this sheet, separators 309 are laminated via adhesive and then reed-shaped positive-electrode sheets 302 each having a strip-shaped area 308 uncoated with the active material and made wider than the strip-shaped uncoated area 307 on the negative electrode are laminated via adhesive. Also, the end of the negative electrode coated with the active material is positioned and laminated in such a way that it projects to the area of the positive electrode uncoated with the active material. Next, an area 313 between the adjacent positive-electrode sheets 302 is cut off and negative and positive electrode terminals are installed, after which they are folded at the strip-shaped uncoated areas 307, 308 to create a folded lithium battery. According to this manufacturing method in Patent Literature 3, the obtained battery has a small capacity per current collector and must have many laminated layers to obtain a large capacity, and consequently reducing the thickness becomes difficult. Also, this battery has a high internal resistance.